Generally, natural gas (NG) presents a viable fuel alternative to fuels, for example, gasoline and diesel fuel. Specifically, NG may be utilized as an alternative fuel to power vehicles and machinery. NG can be liquefied, becoming known as liquefied natural gas (LNG), for transporting to a usage site. At a usage site, cryogenic pumps are usually used to pump LNG to a pressure of approximately 230 psig for dispensing LNG into vehicles and higher pressure cryogenic pumps are used to pressurize LNG to approximately 4000 psig, which is then vaporized to make compressed natural gas (CNG) to dispense CNG into vehicles. The LNG to CNG system is typically referred to as liquefied-to-compressed natural gas (LCNG). A primary concern, therefore, is the ability to quickly and efficiently pump LNG and/or LCNG to the required pressures for dispensing.
Quickly and efficiently pumping LNG and LCNG for dispensing may require multiple cryogenic pumps at a usage site. Typically, cryogenic pumps for LNG and LCNG dispensing are individually located in vacuum insulated vessels. The location of the pumps in vacuum insulated vessels allows for maintaining each pump at an optimum temperature for pumping LNG. That is, pumping LNG or other cryogenic fluids may require the use of pumps at a low temperature to prevent cavitation. When pumps are in contact with ambient temperatures, they may require a time-consuming cooling process prior to starting. When cryogenic pumps are located within vacuum-insulated vessels containing the cryogenic fluid, they do not need to go through the lengthy cooling process, which enables quick-start of the cryogenic pumps for quick LNG and LCNG dispensing operations.
Each insulated vessel may include piping, valves, instrumentation, and vents. Accordingly, with the addition of each cryogenic pump at a usage site comes greater reliability concerns and increased monetary costs associated with each individual insulated vessel and associated piping, valves, instrumentation, and vents. There exists a need, therefore, for a multiple pump system that includes multiple pumps in a single insulated vessel in order to reduce costs associated with individual insulated vessels, while improving reliability and efficiency of pumping LNG and/or LCNG for dispensing at usage sites.